Blood oxygenator

ABSTRACT

An improved blood oxygenator having an oxygen ejector and diffuser for mixing venous blood with oxygen bubbles, and a lattice chamber of spherical beads for accelerating the oxygenation process as the blood/oxygen foam mixture passes through the chamber. The oxygenator also includes an improved non-contaminating defoaming means and a heat exchanger.

United States Patent 1 1 1111 3,898,045

Bowley Aug. 5, 1975 [54] BLOOD ()XYGENATOR 3,513,845 5/1970 Chesnut et31...... 23/2585 X 3,547,591 12/1970 Torres 1 23/2585 [75] 9 Bmvley,Stafford 3,578,411 5 1971 Bentley-ct al... 23/2585 Sprmgs, Conn-3,729,377 4/1973 Leonard 23/2585 X [73] Assigneez Intech Inc. ManchesterConn 3,769,162 10/1973 Brumfleld 23/2585 X 22 i 6, 1972 FOREIGN PATENTSOR APPLICATIONS 1,089,125 9/1960 Germany 23/2585 [211 APPL 295724302.125 6/1971 U.S.S.R 23 2585 [52] 1.8. CI. 23/258-5; 55/255; 55/256;Primary ExaminerBarry Richman 55/527; /5 128/ I 3; 195/l-8; Attorney,Agent, or FirmWeingarten, Maxham &

261/122; 261/D1G. 26; 26l/D1G. 28 Schurgin [51] Int. Cl. A6lm l/03 [58]Field of Search 23/2585; 261/122, DIG. 26,

261/D1G. 28; 55/255, 256-, 527, 528; [57] ABSTRACT 195/ 1 .8; 128/D1G. 3An improved blood oxygenator having an oxygen ejector and diffuser formixing venous blood with oxygen [56] References Cited bubbles, and alattice chamber of spherical beads for UNITED STATES PATENTSaccelerating the oxygenation process as the blood/oxy- 2,934,067 4/1960Calvin 23/2585 gen mixture pfisses thmugh chamber The 3 175 555 3/1965Ling 1 23/2585 oxygenam' @1150 Includes an improved 3:204:63l 9/1965Fields 23/2585 contaminating defoaming means and a heat 3,291,56812/1966 Sautter 1 23/2585 g 3,468,631 9/1969 Raible et a1 23/25853,488,158 1/1970 Bentley 61 al 23/2585 23 Clams, 3 Drawing Flgures BLOODSHEET BLOOD BLOOD OXYGENATOR FIELD OF THE INVENTION This inventionrelates to blood oxygenators and more particularly concerns a simple,relatively inexpensive, disposable blood oxygenator and heat exchangerwhich can be used as a substitute for the lungs of an animal or humanbeing during surgery.

DISCUSSION OF THE PRIOR ART Many devices have been developed forpurposes of oxygenating a patients blood during cardiac or relatedsurgery. Both bubble type and' film type oxygenators are known. Theolder film type devices in which the oxygen must pass through asemi-permeable membrane into the blood are characterized by a very slowrate of oxygenation. The bubble type oxygenators allow for di rectmixing of oxygen bubbles with the oxygen depleted blood. However, usinga sufficient oxygen-blood ratio to produce an acceptable oxygendiffusion rate in such a device tends to create turbulence which causestrauma in the blood cells resulting in hemolysis, a physical breakdownof the blood cells themselves. It is evident that for patient safety,hemolysis must be kept to a minimum.

In bubble type oxygenators there is a relationship be tween bubblesurface area and film resistance to diffusion which should be optimizedin order to maximize the diffusion rate. For a given gas flow rate asmall number of large bubbles has too small a mass transfer area forefficient diffusion, whereas a large number of very small bubbles hassufficient interface area but inefficient diffusion characteristics. Asmight be expected, there exists an optimum size bubble for mostefficient diffusion. Certain well known physical proper ties have abearing upon diffusion rate, an important one being surface filmresistance. At the surface of each oxygen bubble there exists a layer ofoxygen saturated blood. This is an effective boundary layer whichreduces the rate at which the remainder of the oxygen bubble diffusesinto the blood thereby reducing the overall oxygenation rate for a givengas flow rate. This boundary layer is more effective for reducingdiffusion of small bubbles than of large bubbles. Diffusion rate alsorelates to the speed at which bubbles rise through the blood. It maythus be appreciated that attempts have been made to produce bubbles ofrelatively precise size in prior bubble type oxygenators. This givesrise to the present necessity of manufacturing the oxygen bubblediffuser to very close tolerances, a difficult and expensive task atbest.

Apparatus has alsobeen devised where the diffusion chamber is filledwithspherical bodies in order to provide a sufficient agitation forenhanced oxygenation (Russian Pat. No. 302,125). In that device theblood is made to flow in one direction and the oxygen in the oppositedirection through the oxygenator for the stated reason of increasing therate of diffusion. However, turbulence will likely occur when the oxygenand the blood travel in opposite directions and a significant amount ofhemolysis may thereby result. That invention does notprovide a means forpreventing hemolysis due to the movement or vibration of the sphericalbodies in the chamber as the oxygen and blood move through. nor does itprovide for a means to control bubble size. Further, due to thesubstantial resistance to blood flow caused by the opposite directionoxygen flow it would be necessary to pump the blood through the device,effectively sucking the blood from the patient. The dangers inherent inthis practice are obvious. The increased resistance to blood flow tendsto further reduce the efficiency and speed of operation of the Russianoxygenator.

In order to prevent injury to the patient, it is necessary that theblood returned to the arteries be entirely free of any gas bubbles. Itis therefore necessary that the bubble-type oxygenators have additionalprovisions for. defoaming the blood after it has been oxygenated becauseat that point the blood is in the form of a foam. Several previousdevices employ a cylinder packed with chips or fibers soaked in aconventional chemical defoaming or non-wetting agent to break down thebubbles. These structures do not have a uniform density defoamer so thatdefoaming action is different at different locations within thedefoamer. Serious danger to the patient has resulted from this type ofdefoamer fortwo primary reasons. Excess defoaming agent has been knownto have entered the blood, thus contaminating it an'dcausing permanentbrain damage to patients. Also the defoaming agent in the defoamereventu ally becomes exhausted and defoaming action de creases with timeuntil it is too slow to be useful. Proposed methods of time-regulateddischarge of the-defoaming agent are complicated and are notsufficiently reliable. The difficulties associated with the process ofdefoaming severly limit the rate of blood flow through many of thepresently known oxygenators.

The devices of the prior art tend to have a limited flow rateefficiency. Present applications of these devices in cardiac and relatedsurgery indicatethat an improvement in blood flow rate and oxygenationefficiency as well as reliability in defoaming would beof great benefitto the medical profession and to patients.

SUMMARY OF THE INVENTION Generally speaking, the invention hereindisclosed is an improved blood oxygenator for use as a substitute forthe lungs of a patient during cardiac and related surgery. It comprisesa diffuser from which oxygen bubblesof relatively uniform predeterminedsize flow into an ejector filled with blood to make a mixture of bloodand oxygen. This mixture flows through a chamber filled with sphericalhard beads of uniform size forming L a lattice structure. As the oxygenbubbles and the blood move through the bead lattice, oxygen is diffusedinto the'blood and carbon dioxide is removed therefrom. This reaction isfacilitated by frictional contact between the beads and the bubbles inthe blood as they pass through the bead lattice. The resulting actionmay .properly be termed a wiped film bubble oxygenation process. Theoxygenated blood foam thus generated leaves the lattice chamber andenters a defoaming section which has radially and axially uniformdefoaming properties. Several defoamer embodiments are set forth in thedetailed description hereinbelow. The oxygenated defoamed bloodflowsover aheat exchanger in order to effect whatever' temperaturechanges are desired and from there it flows into a calibrated bloodreservoir, ready to return to the arterial system of the patient.

The object of this invention is to provide a simple, relativelyinexpensive, disposable blood oxygenator having significantly improvedblood flow rate and oxygenation efficiency. Additionally,this'oxygenator includes a reliable and constant defoamer whichsubstantially reduces the possibility of dangerous contamination of theblood by chemical antLfoaming agents.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE INVENTIONWith reference now to the drawing there is shown an oxygenator 11,preferably of cylindrical configuration, which comprises ejector 12, adiffuser 13 within the ejector, a lattice chamber 14 formed of a bed ofrigid beads 15 in a cylinder 16, a diverter 17, a defoamer 18, a heatexchanger 21 having a core 22 supported by rings 23 therein, and agraduated reservoir 24.

Ejector 12 is essentially a mixing chamber and bubv.ble pump having sidewalls 25 which are concave inward. Oxygen is supplied through conduit 26to the oxygenator from an outside source (not shown), entering gdiffuser13. Diffuser head 27, shown in detail in FIG.

2, is constructed of a close weave fabric 28 having i -openings ofuniform size secured to a retaining ring 29 ;=attached to the top ofdiffuser 13. The fabric may be Dacron (a registered trademark) or othersuitable materiaI-having relatively uniform openings approximately fortymicrons across. Retaining ring 29 may be any non-corrosive relativelyrigid material such as Lucite (a duPont trademark) or stainless steel.Since a relatively inexpensive, disposable yet sturdy structure iscontemplated, a rigid plastic retaining ring is preferred. Of course,the oxygenator of this invention is not limited to being disposable andthe materials used may vary due to different requirements of the users.

Referring again to FIG. 1, oxygen depleted venous blood enters theejector through conduits 31. Note that there; are two inputs which enterthe bottom of the ejector-at an angle in order to provide a gentleswirling motion. The ejector is normally full of blood and at thebeginning of an operation must be primed with blood or a saline solutionin the normal manner. Oxygen is released from diffuser head.2'7 formingbubbles of substantially uniform size in the blood. As will be seenlater, the preciseness of bubble size is not critical. With the oxygenentering the blood at the location indicated at a relatively highvelocity, the ejector with its concave walls 25 acts as a bubble pump.This structure not only moves the blood through the oxygenator, buteffectively causes the oxygen bubbles to be mixed throughout the bloodat the top of the ejector, as the mixture enters the lattice chamber.

The beads in the lattice chamber are tightly packed and are of uniformsize. These beads are preferably 6 mm in diameter but beads ranging from3 mm to lo mm may be used. The beads may be made of any suitablematerial which provide a relatively smooth, hard surface. While glass isthe substance normally preferred, many other materials such aspolyethylene and polytetrafluoroethylene may be used. The function ofthe lattice chamber will be discussed in detail hereinbelow. A coarsemesh cloth 33 separates the bead bed from the ejector and may be mountedto the bottom of cylinder 16 by a conventional retaining ring or othersuitable means. Cloth 33 has a mesh opening sufficiently small so as toprevent any of the beads from escaping from the lattice chamber whilepermitting free flow of the blood/oxygen mixture from the ejector to thelattice chamber. The top of the lattice chamber is also fitted with asimilar coarse mesh cloth 33 to prevent any of the beads from escapinginto the defoamer.

It has been found that very little trauma is necessary to causehemolysis, that is, injury to the blood cells. For this reason, thebeads in the chamber are preferably secured together to prevent anyvibration or movement within the lattice network. Ultrasonic welding isone good way of accomplishing this desired result Even with the beadssecured together, mesh elements 33 are employed at eitherend of thecylinder 16 in case one of the beads should come loose.

When oxygen bubbles are mixed with blood and diffusion begins to takeplace, a boundary layer of oxygen saturated blood is formed at thesurface of each bubble. This boundary layer resists further diffusion ofoxygen into the oxygen depleted blood lying beyond the layer. To helpcounteract this resistance to complete oxygenation, this inventionteaches that the bubble is made to traverse a long and tortuous paththrough the bead lattice. As the bubble encounters each solid bead,there is a wiping action at the diffusion resistant boundary layer ofthe bubble which physically dislodges or breaks down the boundary layerand results in decreased resistance to the diffusion of oxygen into theblood. The boundary layer reforms as the bubble retreats from eachcollision with a bead but as each oxygenbubble makes its way upwardthrough the bead lattice, it has a large number of collisions withbeads. In the course of each collision, the boundary layer istemporarily broken down and diffusion is facilitated. The rate ofdiffusion of oxygen in the venous blood isincreased by the presence ofthebeads because of the greatly increased surface area for diffusionwhich the beads provide and by the wiping effect produced by thebubble-bead collisions. It may thus be appreciated that the terminologywiped film bubble oxygenation process is quite appropriate.

According to thisinvention, the flow of oxygen and venous blood is inthe same upward direction through the center of the oxygenator, thuseliminating significant resistance to blood flow in opposite directions.In addition, the common directional flow of blood and oxygen bubblesmeans that blood and oxygen *are in contact tzlfirdughout the tirnethatthe blood is flowing through the lattice chamber, thus increasingthe diffusion rate. Also, the co-directional flowof the blood and oxygenavoids the turbulence which would result from the collision of twooppositely directed flows.

According to the invention there a're'uniform size passageways betweenthe beads 15 inthe lattice chamber 14 because the beads themselves areuniform in size. These constricted passageways regulate to a veryclosetolerance the size of the oxygen bubbles which can pass through thebead lattice. It is well known in the art that in bubble typeoxygenators there is a balance between bubble area and film resistancewhich is difficult to achieve as has previously been stated. It isnecessary to maintain a balance in bubble size in order 5. to maximizediffusion and this must be done accurately. In conventional bubble typeoxygenators, th'is i's"at'- tempted by means of a diffuser with openingsmanufactured to very close tolerances. In the presentinvention, theuniform spacingsbetween the beads can be designed to permit only bubblesof the desired size to proceed through the bead lattice therebyproviding maximim diffusion efficiency. Larger bubbles will be separatedas they 'pass through the restricted passageways between the beads,thereby accomplishing the desired effect. Consequently, fabric 28 ondiffuser'head 27 need not'be manufactured to extremely close tolerancessince the bead bed will reduce bubble size as'the mixture passes'throughit.

It is not apparent that several factors of the present inventioncontribute to increased diffusion speed and efficiency; Among thesefactors are the cumulatively large surface area of the heads, the wipingaction produced by contact between the pliable bubbles and the hardbeads, the'long mutual contact time resulting from co-directional flowof blood and oxygen and the long path of travel which results from thepresence'of the closely packed beads. Such factors enable the oxygenatorof the present'invention to be operated at a'lower oxygen/blood flowratio than is possible in conventional oxygenato'rs. [t is well known inthe art that when the oxygen/blood flow ratio is decreased, theturbulence which occurs in the blood-oxygen mixture also decreases. Whenturbulence decreases, hemolysis is significantly reduced. Thusanimportant effect of the present invention is greatly reducedhemolysis, while maintaining an overall high diffusion efficiency.

The oxygenated blood foam contacts diverter 17 directly from the top oflattice chamber 14. The diverter consists of a concave conical surfacepreferably made of clear plastic although other shapes and materials maybe used. The foam is directed'outward by the diverter and entersdefoamer 18 which surrounds the top portion of the lattice chamber abovethe heat exchanger. Note that the defoamer fabric extends to the centerof the oxygenator between the top of the lattice chamber and thediverter.

With reference not to FIG. 3, a top view of defoamer 18 is shown. Itconsists of a woven cloth 34 which is wound around the upper portion ofthe lattice chamber a predetermined number of turns in order to insureradial uniformity and consistency in production. Defoaming may beachieved in the well-known manner wherein bubbles containing carbondioxide and oxygen collapse on fibers which have been coated by sprayingor dipping with a chemical antifoam or nonwetting agent. A preferredembodiment of the defoamer is to wrap the lattice chamber with amaterial comprising two alternating layers of fabric, one wetting andone nonwetting. In this embodiment the bubbles are pulled apart by beingrepelled from the non-wetting material and attracted to the wettingmaterial whereon it col lapses and drains to the reservoir 24. Analternative preferred embodiment of the defoamer is to use a cloth wovenof wetting fibers running horizontally and nonwetting fibers runningvertically. The bubbles are repelled and attracted as stated above,causing the bubbles to collapse in a single vertical plane drain to thereservoir. These two preferred embodiments utilize fibers whose wettingand non-wetting properties are inherent in the materials themselvesratherthan the result of treatment with chemical agents. Examples ofnonwetting materials are nylon and polytetrafluoroethylene, whilewetting materials may be glass fiber or fibersfrom the polycarbonatefamily such as Lexan (a registered trademark). These embodiments havethe advantage of stability, that is the non-wetting and wettingproperties of the fibers are constant in time. Further, there is nolikelihood of dangerous contamination of the patients blood withanti-foam agent. The cloth of the defoamer is wound relatively tightlyaround the lattice chamber so thateach successive turn contacts theadjacent turns and there'is radial uniformity from the lattice chamberoutw'ardto the wall of the oxygenator. The 'defoamerfillsall of thespace between cylinder 16 and the walls of the oxygenator which liesbetween the heat exchanger and the diverter.

Carbon dioxide and excess oxygen released from the blood as it isdefoamed is' exhausted from the oxygenator through vent 35 in the top ofthe defoamer. The vent may be equipped with a'conventionalbacteriological filter (not shown) to prevent possible contaminationofthe atmosphere in the operating room..

The oxygenated blood drains from the defoamer and is allowed to flowover the heat exchanger 21. The heat exchanger is an annular cylindricalcontainerwith an annular core 22 of closedcell foam filling the bulk ofthe interior thereof. The core is held in place by means of rings 23 atthe top and bottom of the'container. Heated or cooled water ispumpedthrough the heat exchanger, entering through conduit 36 andleaving through'conduit 37. The bloodis th'e'reby maintained at apredetermined desired temperature. Fluid other than water could be usedif desired; This particular configuration for the heat e'xchangerpermitsa large surface area for rapid temperature adjustment ofthe bloodflowing over its sides while having a reduced interior volume to permitrapid fluid exchange within it. t

The oxygenated blood of desired temperature is stored in a reservoir' 24which preferably has transparent walls. The reservoir is an annularconfiguration and surrounds the ejector and diffuser and the lower endof the lattice chamber. The reservoir'is calibratedtscale 38) as tovolume in order that theamount of blood available can easilybe'monitored 'duringthe operation. The oxygenated blood is removed fromthe reservoir through tubing 40 controlled by conventional ball-typecheck valve 39 which closes the outlet when insufficient blood ispresent in the reservoir. This prevents any air from getting into thepatients arterial system in an emergency situation when the bloodreservoir becomes empty. Note that the heat exchanger resides within thereservoir in order to 'rnaintain the'blood temperature as desired.

A ring 41 is secured to the top of the oxygenator to provide forattachment of the unit to a ring stand holder. Preferably the main shelland most of the interior parts of this oxygenator are made ofsubstantially rigid transparent plastic so that its proper operation maybe observed at all times. The plastic elements may be secured togetherby adhesive or by other suitable means. By being made'of plastic it isdisposable, inex pensive to make and shatter resistant. The overall sizeof this oxygenator is approximately 18 inches in height and 7 inches indiameter for adults/Because thevolume necessary for babies is muchlessfa reduced size oxygenator is available for pediatric purposes. Ofcourse, the size specified above is by way of example only and is in noway limiting.

The invention herein disclosed is a very compact. vertically hungoxygenator. Installation time and operator training are minimal sincethe device is presterilized and disposable, while being very simple toset up and operate. Those skilled in the art will readily appreciatethat various modifications and improvements to this oxygenator may bemade to suit particular requirements which are within the scope of theinvention.

What is claimed is:

l. A blood oxygenator comprising:

a housing;

means within said housing for mixing blood and oxygen together to form afoam and for pumping the foam through said oxygenator, said mixing andpumping means having at least one blood inlet port at one end and ablood foam outlet at the opposite end;

oxygen diffusing means within said mixing and pumping means, said oxygendiffusing means having an oxygen inlet port and having an oxygen outletspaced from either end of said mixing and pumping means, said oxygendiffusing means further comprising: means at said oxygen outlet fordischarging oxygen into the blood in said mixing and pumping means inthe form of bubbles;

an elongated chamber within said housing, the walls of said chamberbeing laterally spaced from the interior surfaces of said housing;

a lattice bed comprising a multiplicity of hard beads of substantiallyuniform size being tightly packed within and substantially filling saidchamber to thereby provide a relatively large collision surface areawithin said chamber and a plurality of tortuous paths therethrough, eachof which is substantially longer than said chamber, said chamber havingan outlet and having an inlet coupled to said blood foam outlet of saidmixing and pumping means;

means for maintaining said lattice bed in tightly packed configurationwithin said chamber;

defoaming means within said housing adjacent said outlet of saidchamber, said blood foam being separated into gases and fluid bloodwithin said defoaming means;

fluid blood storage means below and in communication with said defoamingmeans; and

fluid blood outlet means mounted in the bottom of said storage means.

2. The oxygenator recited in claim 1 and further comprising meanslocated at the outlet of said chamber for diverting the oxygenated bloodfoam away from the top of said chamber and to said defoaming means.

3. The oxygenator recited in claim 1 and further comprising an exhaustport for exhausting carbon dioxide and excess oxygen from saidoxygenator.

4. The oxygenator recited in claim 1 wherein said blood inlet portenters said mixing and pumping means at an angle relative to the axis ofsaid elongated chamber to provide gentle swirling action to the blood.

5. The oxygenator recited in claim 1 wherein said means for maintainingsaid lattice bed in tightly packed configuration comprises asubstantially rigid coarse mesh cloth'at each end of said chamberconfining said beads therein.

6. The oxygenator recited in claim 1 wherein said means for maintainingsaid lattice bed in tightly packed configuration comprises means forminga rigid bond between adjacent contacting beads within said chamher.

7. The oxygenator recited in claim 1 wherein said means for dischargingoxygen into the blood in the form of bubbles comprises a fabric coveringsaid oxygen outlet of said oxygen diffusing means, said fabric having amultiplicity of openings therethrough of substantially uniform size.

8. The oxygenator recited in claim 1 and further comprising safety valvemeans in said fluid blood outlet means operative to remain open onlywhen there is fluid in said fluid blood storage means.

9. The oxygenator recited in claim 1 and further comprising means withinsaid housing to adjust the blood temperature for reentry into a patient,said temperature adjusting means having an inlet and an outlet fortemperature adjusting fluid to pass therethrough.

10. The oxygenator recited in claim 9 wherein said means for adjustingblood temperature is an annular cylindrical container surrounding saidmixing and pumping means and wherein said fluid blood storage means isan annular cylindrical chamber surrounding said mixing and pumpingmeans, said temperature adjusting means container being located withinsaid fluid blood storage means chamber.

11. The oxygenator recited in claim 1 wherein said defoaming meanscomprises:

multiple layers of cloth wherein each such layer is in confrontingrelationship and touches the next adjacent layer, said cloth beingformed of a multiplicity of fibers, a first portion of said fibershaving nonwetting characteristics relative to blood, and a secondportion of said fibers having a lesser degree of non-wettingcharacteristics relative to blood than said first portion of saidfibers.

12. The oxygenator recited in claim 11 wherein:

said mixing and pumping means is elongated and has a longitudinalmid-point cross section which is substantially less than the crosssection thereof at said outlet end; and

said oxygen outlet of said oxygen diffusing means is locatedsubstantially at said longitudinal mid-point of said mixing and pumpingmeans.

13. A blood oxygenator comprising:

a housing;

means within said housing for mixing blood and oxygen together to form afoam and for pumping the foam through said oxygenator, said mixing andpumping means having at least one blood inlet port at one end and ablood foam outlet at the opposite end;

oxygen diffusing means within said mixing and pumping means, said oxygendiffusing means having an oxygen inlet port and having an oxygen outletspaced from either end of said mixing and pumping means, said oxygendiffusing means further comprising:

means at said oxygen outlet for discharging oxygen into the blood insaid mixing and pumping means in the form of bubbles;

an elongated chamber within said housing, the walls of said chamberbeing laterally spaced from the interior surfaces of said housing;

a lattice bed comprising a multiplicity of hard beads of substantiallyuniform size being tightly packed within and substantially filling saidchamber to thereby provide a relatively large collision surface areawithin said chamber and a plurality of tortuous paths therethrough, saidchamber having an outlet and having an inlet coupled to said blood foamoutlet of said mixing and pumping means; means for maintaining saidlattice bed in tightly packed configuration within said chamber;defoaming means within said housing adjacent said outlet of saidchamber, said blood foam being separated into gases and fluid bloodwithin said defoaming means, said defoaming means comprising: multiplelayers of cloth wherein each such layer is in confronting relationshipand touches the next adjacent layer, said cloth being formed of amultiplicity of fibers, a first portion of said fibers havingnon-wetting characteristics relative to blood, and a second portion ofsaid fibers having a lesser degree of nonwetting characteristicsrelative to blood than said first portion of said fibers; fluid bloodstorage means below and in communication with said defoaming means; andfluid blood outlet means mounted in the bottom of said storage means,

14. The oxygenator recited in claim 13 wherein said first portion ofsaid fibers having non-wetting characteristics comprises first layers ofsaid multiple layers of cloth, and said second portion of said fibershaving a lesser degree of non-wetting characteristics comprises secondlayers of said multiple layers of cloth, one of said first layers ofcloth being located between two adjacent confronting second layers ofcloth in alternating fashion throughout said defoaming means.

15. The oxygenator recited in claim 13 wherein said multiple layers ofcloth fully occupy the space between the walls of said chamber and theinterior surfaces of said housing adjacent to the outlet end of saidchamber.

16. The oxygenator recited in claim 13 wherein said non-wettingcharacteristics are provided in said first portion of said fibers bymeans of a coating of nonwetting material.

17. The oxygenator recited in claim 13 wherein each of said layers ofcloth is woven wherein said first portion of said fibers havingnon-wetting characteristics are oriented in one direction and saidsecond portion of said fibers having a lesser degree of non-wettingcharacteristics are cross woven with said first portion of said fibers.

18. The oxygenator recited in claim 17 wherein said first portion ofsaid fibers having non-wetting characteristics are arranged to lie alongan axis substantially parallel to the axis of said elongated chamber topermit efficient draining of the liquid from said blood foam by force ofgravity.

19. The oxygenator recited in claim 13 wherein the non-wettingcharacteristics of said first portion of said fibers is inherent in saidfibers, and the lesser degree of non-wetting characteristics of saidsecond portion of said fibers is inherent in said fibers.

20. The oxygenator recited in claim 19 wherein:

said first portion of said fibers having non-wetting characteristicsrelative to blood is a member of the group consisting of glass andpolycarbonates; and said second portion of said fibers having a lesserdegree of non-wetting characteristics relative to blood is a member ofthe group consisting of nylon and polytetrafluoroethylene.

21. A blood oxygenator comprising:

a housing;

means within said housing for mixing blood and oxygen together to form afoam and for pumping the foam through said oxygenator, said mixing andpumping means having at least one blood inlet port at one end and ablood foam outlet at the opposite end, said mixing and pumping meansbeing elongated and having a midpoint cross section which issubstantially less than the cross section thereof at said outlet end;

oxygen diffusing means within said mixing and pumping means, said oxygendiffusing means having an oxygen inlet port and having an oxygen outletspaced from either end of said mixing and pumping means and locatedsubstantially at said mid-point thereof, said oxygen diffusing meansfurther comprising: means at said oxygen outlet for discharging oxygeninto the blood in said mixing and pumping means in the form of bubbles,the velocity of the oxygen being converted to a foam pressure at saidoutlet of said mixing and pumping means due to the expanding crosssection thereof from the point of entry of the oxygen bubbles to saidoutlet;

an elongated chamber within said housing, the walls of said chamberbeing laterally spaced from the interior surfaces of said housing;

a lattice bed comprising a multiplicity of hard beads of substantiallyuniform size being tightly packed within and substantially filling saidchamber to 7 thereby provide a relatively large collision surface areawithin said chamber and a plurality of tortuous paths therethrough, saidlattice chamber having an outlet and having an inlet coupled to saidblood foam outlet of said mixing and pumping means;

means for maintaining said lattice bed in tightly packed configurationwithin said chamber;

defoaming means within said housing adjacent said outlet of said latticechamber, said blood foam being separated into gases and fluid bloodwithin said defoaming means;

fluid blood storage means within said housing and located below saiddefoaming means; and

fluid blood outlet means mounted in the bottom of said storage means.

22. The oxygenator recited in claim 21 wherein the blood foam outlet ofsaid mixing and pumping means has substantially the same cross sectionas said inlet of said elongated lattice chamber.

23. The oxygenator recited in claim 22 wherein said oxygen outlet ofsaid oxygen diffusing means is substantially smaller in cross sectionalarea than the cross section of said mixing and pumping means lying inthe same plane as said oxygen outlet, whereby the mass flow of oxygenfrom said oxygen outlet is less than blood through said mixing andpumping means at the same plane as said oxygen outlet.

1. A BLOOD OXYGENATOR COMPRISING: A HOUSING MEANS WITHIN SAID HOUSINGFOR MIXING BLOOD AND OXYGEN TOGETHER TO FORM A FOAM AND FOR PUMPING THEFOAM THROUGH SAID OXYGENATOR, SAID MIXING AND PUMPING MEANS HAVING ATLEAST ONE BLOOD INLET PORT AT ONE END AND A BLOOD FOAM OUTLET AT THEOPPOSITE END, OXYGEN DIFFUSING MEANS WITHIN SAID MIXING AND PUMPINGMEANS, SAID OXYGEN DIFFUSING MEANS HAVING AN OXYGEN INLET PORT ANDHAVING AN OXYGEN OUTLET SPACED FROM EITHER END OF SAID MIXING ANDPUMPING MEANS, SAID OXYGEN DIFFUSING MEANS FURTHER COMPRISING: MEANS ATSAID OXYGEN OUTLET FOR DISCHARGING OXYGEN INTO THE BLOOD IN SAID MIXINGAND PUMPING MEANS IN THE FORM OF BUBBLES, AN ELONGATED CHAMBER WITHINSAID HOUSING, THE WALLS OF SAID CHAMBER BEING LATERALLY SPACED FROM THEINTERIOR SURFACES OF SAID HOUSING, A. LATTICE BED COMPRISING AMULTIPLICITY OF HARD BEADS OF SUBSTANTIALLY UNIFORM SIZE BEING TIGHTLYPACKED WITHIN AND SUBATANTIALLY FILLING SAID CHAMBER TO THEREBY PROVIDEA RELATIVELY LARGE COLLISION SURFACE AREA WITHIN SAID CHAMBER AND APLURALITY OF TORTUOUS PATHS THERETHROUGH, EACH OF WHICH IS SUBSTANTIALLYLONGER THAN SAID CHAMBER, SAID CHAMBER HAVING AN OUTLET AND HAVING ANINLET COUPLED TO SAID BLOOD FOAM OUTLET OF SAID MIXING AND PUMPINGMEANS, MEANS FOR MAINTAINING SAID LATTICE BED IN TIGHTLY PACKEDCONFIGURATION WITHIN SAID CHAMBER, DEFOAMING MEANS WITHIN SAID HOUSINGADJACENT SAID OUTLET OF SAID CHAMBER, SAID BLOOD FOAM BEING SEPARATEDINTO GASES SAID FLUID BLOOD WITHIN SAID DEFOAMING MEANS, FLUID BLOODSTORAGE MEANS BELOW AND IN COMMUNICATION WITH SAID DEFOAMING MEANS, ANDFLUID BLOOD OUTLET MEANS MOUNTED IN THE BOTTOM OF SAID STORAGE MEANS, 2.The oxygenator recited in claim 1 and further comprising means locatedat the outlet of said chamber for diverting the oxygenated blood foamaway from the top of said chamber and to said defoaming means.
 3. Theoxygenator recited in claim 1 and further comprising an exhaust port forexhausting carbon dioxide and excess oxygen from said oxygenator.
 4. Theoxygenator recited in claim 1 wherein said blood inlet port enters saidmixing and pumping means at an angle relative to the axis of saidelongated chamber to provide gentle swirling action to the blood.
 5. Theoxygenator recited in claim 1 wherein said means for maintaining saidlattice bed in tightly packed configuration comprises a substantiallyrigid coarse mesh cloth at each end of said chamber confining said beadstherein.
 6. The oxygenator recited in claim 1 wherein said means formaintaining said lattice bed in tightly packed configuration comprisesmeans forming a rigid bond between adjacent contacting beads within saidchamber.
 7. The oxygenator recited in claim 1 wherein said means fordischarging oxygen into the blood in the form of bubbles comprises afabric covering said oxygen outlet of said oxygen diffusing means, saidfabric having a multiplicity of openings therethrough of substantiallyuniform size.
 8. The oxygenator recited in claim 1 and furthercomprising safety valve means in said fluid blood outlet means operativeto remain open only when there is fluid in said fluid blood storagemeans.
 9. The oxygenator recited in claim 1 and further comprising meanswithin said housing to adjust the blood temperature for reentry into apatient, said temperature adjusting means having an inlet and an outletfor temperature adjusting fluid to pass therethrough.
 10. The oxygenatorrecited in claim 9 wherein said means for adjusting blood temperature isan annular cylindrical container surrounding said mixing and pumpingmeans and wherein said fluid blood storage means is an annularcylindrical chamber surrounding said mixing and pumping means, saidtemperature adjusting means container being located within said fluidblood storage means chamber.
 11. The oxygenator recited in claim 1wherein said defoaming means comprises: multiple layers of cloth whereineach such layer is in confronting relationship and touches the nextadjacent layer, said cloth being formed of a multiplicity of fibers, afirst portion of said fibers having non-wetting characteristics relativeto blood, and a second portion of said fibers having a lesser degree ofnon-wetting characteristics relative to blood than said first portion ofsaid fibers.
 12. The oxygenator recited in claim 11 wherein: said mixingand pumping means is elongated and has a longitudinal mid-point crosssection which is substantially less than the cross section thereof atsaid outlet end; and said oxygen outlet of said oxygen diffusing meansis located substantially at said longitudinal mid-point of said mixingand pumping means.
 13. A blood oxygenator comprising: a housing; meanswithin said housing for mixing blood and oxygen together to form a foamand for pumping the foam through said oxygenator, said mixing andpumping means having at least one blood inlet port at one end and ablood foam outlet at the opposite end; oxygen diffusing means withinsaid mixing and pumping means, said oxygen diffusing means having anoxygen inlet port and having an oxygen outlet spaced from either end ofsaid mixing and pumping means, said oxygen diffusing means furthercomprising: means at said oxygen outlet for discharging oxygen into theblood in saId mixing and pumping means in the form of bubbles; anelongated chamber within said housing, the walls of said chamber beinglaterally spaced from the interior surfaces of said housing; a latticebed comprising a multiplicity of hard beads of substantially uniformsize being tightly packed within and substantially filling said chamberto thereby provide a relatively large collision surface area within saidchamber and a plurality of tortuous paths therethrough, said chamberhaving an outlet and having an inlet coupled to said blood foam outletof said mixing and pumping means; means for maintaining said lattice bedin tightly packed configuration within said chamber; defoaming meanswithin said housing adjacent said outlet of said chamber, said bloodfoam being separated into gases and fluid blood within said defoamingmeans, said defoaming means comprising: multiple layers of cloth whereineach such layer is in confronting relationship and touches the nextadjacent layer, said cloth being formed of a multiplicity of fibers, afirst portion of said fibers having non-wetting characteristics relativeto blood, and a second portion of said fibers having a lesser degree ofnon-wetting characteristics relative to blood than said first portion ofsaid fibers; fluid blood storage means below and in communication withsaid defoaming means; and fluid blood outlet means mounted in the bottomof said storage means.
 14. The oxygenator recited in claim 13 whereinsaid first portion of said fibers having non-wetting characteristicscomprises first layers of said multiple layers of cloth, and said secondportion of said fibers having a lesser degree of non-wettingcharacteristics comprises second layers of said multiple layers ofcloth, one of said first layers of cloth being located between twoadjacent confronting second layers of cloth in alternating fashionthroughout said defoaming means.
 15. The oxygenator recited in claim 13wherein said multiple layers of cloth fully occupy the space between thewalls of said chamber and the interior surfaces of said housing adjacentto the outlet end of said chamber.
 16. The oxygenator recited in claim13 wherein said non-wetting characteristics are provided in said firstportion of said fibers by means of a coating of non-wetting material.17. The oxygenator recited in claim 13 wherein each of said layers ofcloth is woven wherein said first portion of said fibers havingnon-wetting characteristics are oriented in one direction and saidsecond portion of said fibers having a lesser degree of non-wettingcharacteristics are cross woven with said first portion of said fibers.18. The oxygenator recited in claim 17 wherein said first portion ofsaid fibers having non-wetting characteristics are arranged to lie alongan axis substantially parallel to the axis of said elongated chamber topermit efficient draining of the liquid from said blood foam by force ofgravity.
 19. The oxygenator recited in claim 13 wherein the non-wettingcharacteristics of said first portion of said fibers is inherent in saidfibers, and the lesser degree of non-wetting characteristics of saidsecond portion of said fibers is inherent in said fibers.
 20. Theoxygenator recited in claim 19 wherein: said first portion of saidfibers having non-wetting characteristics relative to blood is a memberof the group consisting of glass and polycarbonates; and said secondportion of said fibers having a lesser degree of non-wettingcharacteristics relative to blood is a member of the group consisting ofnylon and polytetrafluoroethylene.
 21. A blood oxygenator comprising: ahousing; means within said housing for mixing blood and oxygen togetherto form a foam and for pumping the foam through said oxygenator, saidmixing and pumping means having at least one blood inlet port at one endand a blood foam outlet at the opposite end, said mixing and pumpingmeans being elongated and having a Midpoint cross section which issubstantially less than the cross section thereof at said outlet end;oxygen diffusing means within said mixing and pumping means, said oxygendiffusing means having an oxygen inlet port and having an oxygen outletspaced from either end of said mixing and pumping means and locatedsubstantially at said mid-point thereof, said oxygen diffusing meansfurther comprising: means at said oxygen outlet for discharging oxygeninto the blood in said mixing and pumping means in the form of bubbles,the velocity of the oxygen being converted to a foam pressure at saidoutlet of said mixing and pumping means due to the expanding crosssection thereof from the point of entry of the oxygen bubbles to saidoutlet; an elongated chamber within said housing, the walls of saidchamber being laterally spaced from the interior surfaces of saidhousing; a lattice bed comprising a multiplicity of hard beads ofsubstantially uniform size being tightly packed within and substantiallyfilling said chamber to thereby provide a relatively large collisionsurface area within said chamber and a plurality of tortuous pathstherethrough, said lattice chamber having an outlet and having an inletcoupled to said blood foam outlet of said mixing and pumping means;means for maintaining said lattice bed in tightly packed configurationwithin said chamber; defoaming means within said housing adjacent saidoutlet of said lattice chamber, said blood foam being separated intogases and fluid blood within said defoaming means; fluid blood storagemeans within said housing and located below said defoaming means; andfluid blood outlet means mounted in the bottom of said storage means.22. The oxygenator recited in claim 21 wherein the blood foam outlet ofsaid mixing and pumping means has substantially the same cross sectionas said inlet of said elongated lattice chamber.
 23. The oxygenatorrecited in claim 22 wherein said oxygen outlet of said oxygen diffusingmeans is substantially smaller in cross sectional area than the crosssection of said mixing and pumping means lying in the same plane as saidoxygen outlet, whereby the mass flow of oxygen from said oxygen outletis less than blood through said mixing and pumping means at the sameplane as said oxygen outlet.